The rapid development of smaller, lighter, and higher performance communication and other electronic equipment has required the development of high performance and large capacity batteries to power such equipment. The demands for large capacity batteries have fostered investigation of rechargeable lithium batteries. The rechargeable lithium battery employs a non-aqueous electrolyte including lithium salts dissolved in organic solvents.
There have been investigations on various additives for forming a layer on a surface of a negative electrode in order to improve battery performance. One attempt is that pyrrole, thiophene, or vinylene carbonate is added to the electrolyte. These compounds polymerize during charge and discharge to form a thin polymer layer on a surface of a negative active material and improve the battery's cycle life characteristics. Another attempt is that anisole is added to the electrolyte in order to improve the battery's safety characteristics.
However, the method for forming the thin polymer layer has shortcomings in that it is difficult to control the thin layer, and there are concerns about volume expansion of the battery. The anisole forms a high-resistance polymer layer on the negative electrode after the oxidation of the positive electrode, causing deteriorating battery performance factors such as cycle life characteristics. Thus, attempts to use additives for forming layers can improve a particular battery performance factor, but at the cost of a deterioration of one or more different performance factors.
Other attempts have been made to address such shortcomings by adding ethyl maleimide or methyl maleimide, but there has not been substantial use in batteries.